Small Animal Radiology and Ultrasound: A Diagnostic Atlas and Text

588 Small Animal Radiolo g y and Ultrasono graphy
S U B C U TA N E O U S A N D I N T R A A RT I C U L A R G A S
The most common cause of gas or air accumulation within the soft tissues is an external
wound. In rare cases, gas may accumulate in the subcutaneous tissues secondary to infection.
Regardless of cause, gas usually accumulates or dissects along fascial planes and
appears as linear radiolucencies. 669,670 Large gas pockets may be seen occasionally.
Intraarticular gas accumulation may occur with laceration from compound fracture.
Its presence suggests the possibility of septic inflammation. Another cause of intraarticular
gas is the vacuum phenomeon. 671,672 This is usually due to abnormal radiographic positioning
stresses or joint instability.
S O F T-TISSUE M I N E R A L I Z AT I O N
Soft-tissue mineralization or calcification may result from dystrophic or metastatic mineralization.
326,673,674 Tumors, chronic infections, and hematomas may calcify and produce
discrete areas of mineral density. 675,676 Ossifying myositis, which is progressive ossification
of muscle and connective tissue, may be seen also. 677-681 The pattern of mineralization is
not specific, and the size, shape, and location of the entire lesion, including its soft-tissue
component, are important in determining a radiographic diagnosis. Endocrinopathies,
Fig. 4-142 A 9-year-old neutered male Shar Pei was evaluated for an
acute lameness of the left hind limb. The lateral radiograph of the
tarsal region reveals multiple pairs of fine, parallel calcifications caudal
to the metatarsal bones (arrows) as well as lateral to the fibula and caudal
to the tibia. Serum analysis revealed significant hypothyroidism.
Diagnosis: Vascular calcification secondary to hypothyroidism. The
lameness was due to a stifle injury.